U.S. patent application number 14/256030 was filed with the patent office on 2015-02-12 for light emitting device.
This patent application is currently assigned to Lextar Electronics Corporation. The applicant listed for this patent is Lextar Electronics Corporation. Invention is credited to Yung-Long Jian, Chen-Yi Su.
Application Number | 20150042241 14/256030 |
Document ID | / |
Family ID | 50981011 |
Filed Date | 2015-02-12 |
United States Patent
Application |
20150042241 |
Kind Code |
A1 |
Su; Chen-Yi ; et
al. |
February 12, 2015 |
LIGHT EMITTING DEVICE
Abstract
A light emitting device comprising a carrier board, a first
group of light emitting elements, a second group of light emitting
elements and a driver circuit. The first group of light emitting
elements includes a plurality of first LEDs disposing on the
carrier board and are used for emitting a first color temperature
light. The second group of light emitting elements includes a
plurality of second LEDs disposing on the carrier board and are
used for emitting a second color temperature light. The first LEDs
and the second LEDs are disposed in an alternative arrangement. The
driver circuit output a first and a second driving current to
drives the first LED and the second LED respectively. When the
first driving current is the maximum, the second driving current is
the minimum, and vice versa. The minimum of the first driving
current and the second driving current is not zero.
Inventors: |
Su; Chen-Yi; (Taoyuan City,
TW) ; Jian; Yung-Long; (New Taipei City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Lextar Electronics Corporation |
Hsinchu |
|
TW |
|
|
Assignee: |
Lextar Electronics
Corporation
Hsinchu
TW
|
Family ID: |
50981011 |
Appl. No.: |
14/256030 |
Filed: |
April 18, 2014 |
Current U.S.
Class: |
315/294 |
Current CPC
Class: |
H05B 45/46 20200101;
H05B 45/20 20200101 |
Class at
Publication: |
315/294 |
International
Class: |
H05B 33/08 20060101
H05B033/08 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 12, 2013 |
TW |
102128860 |
Claims
1. A light emitting device, comprising: a carrier board; a first
group of light emitting elements comprising a plurality of first
LEDs disposed on the carrier board and used for emitting a first
color temperature light; a second group of light emitting elements
comprising a plurality of second LEDs disposed on the carrier board
and used for emitting a second color temperature light, wherein the
first LEDs and the second LEDs are disposed in an alternative
arrangement; and a driver circuit used for outputting a first
driving current and a second driving current to drive the first
LEDs and the second LEDs respectively, wherein when the first
driving current is the maximum, the second driving current is the
minimum but not equal to zero, and when the second driving current
is the maximum, the first driving current is the minimum but not
equal to zero.
2. The light emitting device according to claim 1, further
comprising a color temperature controlling interface coupled to the
driver circuit and used for controlling magnitudes of the first
driving current and the second driving current.
3. The light emitting device according to claim 2, wherein in a
first color temperature mode selected through the color temperature
controlling interface, when the first driving current is the
maximum, the second driving current is the minimum but not equal to
zero.
4. The light emitting device according to claim 2, wherein in a
second color temperature mode selected through the color
temperature controlling interface, when the second driving current
is the maximum, the first driving current is the minimum but not
equal to zero.
5. The light emitting device according to claim 1, wherein the
first group of light emitting elements and the second group of
light emitting elements are in parallel.
6. The light emitting device according to claim 5, wherein the
first LEDs are in parallel.
7. The light emitting device according to claim 5, wherein the
second LEDs are in parallel.
8. The light emitting device according to claim 1, wherein color
temperature of the first color temperature light is different from
that of the second color temperature light.
9. The light emitting device according to claim 8, wherein the
first color temperature light is warm white, and the second color
temperature light is cool white.
10. The light emitting device according to claim 8, wherein the
first color temperature light is cool white, and the second color
temperature light is warm white.
Description
[0001] This application claims the benefit of Taiwan application
Serial No. 102128860, filed Aug. 12, 2013, the subject matter of
which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates in general to a light emitting device,
and more particularly to a light emitting diode (LED) device.
[0004] 2. Description of the Related Art
[0005] Light emitting diode (LED) having the advantages of high
light emitting efficiency, long lifespan, robustness, fast response
rate and high reliability has become a commonly used light source
in lighting and electronic device. In practical use, several LEDs
are combined together to increase brightness and efficiency for
emitting light.
[0006] In response to the trend of slimness, lightweight and
compactness of electronic device, the design of LED light source is
also directed towards lightweight and slimness. However, when the
distance between the LED body and the lamp mask is too short, the
emitting light will generate bright band and dark band, the so
called "Hotspot", and deteriorate light uniformity. Furthermore,
brightness and lifespan may even be reduced because the heat is
over concentrated.
SUMMARY OF THE INVENTION
[0007] The invention is directed to a light emitting device with
excellent light uniformity.
[0008] According to one embodiment of the present invention, a
light emitting device comprising a carrier board, a first group of
light emitting elements, a second group of light emitting elements
and a driver circuit is provided. The first group of light emitting
elements comprises a plurality of first LEDs disposed on the
carrier board and used for emitting the first color temperature
light. The second group of light emitting elements comprises a
plurality of second LEDs disposed on the carrier board and used for
emitting the second color temperature light. The first LEDs and the
second LEDs are disposed in an alternative arrangement. The driver
circuit outputs a first driving current and a second driving
current to drive the first LEDs and the second LEDs respectively.
When the first driving current is the maximum, the second driving
current is the minimum but not equal to zero. When the second
driving current is the maximum, the first driving current is the
minimum but not equal to zero.
[0009] The above and other aspects of the invention will become
better understood with regard to the following detailed description
of the preferred but non-limiting embodiment (s). The following
description is made with reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic diagram of a light emitting device
according to an embodiment of the invention.
[0011] FIG. 2 is an equivalent circuit diagram of the light
emitting device of
[0012] FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0013] Referring to FIG. 1, a schematic diagram of a light emitting
device according to an embodiment of the invention is shown. The
light emitting device 10 comprises a carrier board 100, a first
group of light emitting elements 110, a second group of light
emitting elements 120 and a driver circuit 130. The first group of
light emitting elements is formed by a plurality of first LEDs 111
and is used for emitting a first color temperature light. The
second group of light emitting elements is formed by a plurality of
second LEDs 112 and is used for emitting a second color temperature
light. Two groups of LEDs with different color temperatures are
used to mix light. The first LEDs 111 and the second LEDs 112,
which can be realized by the same or different LEDs, are disposed
on the carrier board 100 at an interval in an alternative
arrangement. The driver circuit 130 is disposed on the carrier
board 110 for providing currents to the first and the second light
emitting units 110 and 120. In the present embodiment, the first
LEDs 111 and the second LEDs 112 are arranged in a straight line to
form a light bar. In other embodiment, the first LEDs 111 and the
second LEDs 112 can also be arranged as a plane, a circle or any
other shapes. In the present embodiment, the quantity of first LEDs
111 is the same as that of second LEDs 112 (both are 5 LEDs).
However, the quantity of the first LEDs 111 can be different that
of the second LEDs 112 in other embodiments. For instance, 4 second
LEDs 112 are alternately arranged among 5 first LEDs 111. The
invention does not restrict the quantity and arrangement shape of
LEDs, and any quantities and arrangement shapes can do as long as
the first LEDs 111 and the second LEDs 112 are disposed in an
alternative arrangement.
[0014] Referring to FIG. 2, an equivalent circuit diagram of the
light emitting device of FIG. 1 is shown. The first group of light
emitting elements 110 and the second group of light emitting
elements 120 are in parallel. In an embodiment, each first LED 111
of the first group of light emitting elements 110 is in parallel,
and each second LED 112 of the second group of light emitting
elements 110 is also in parallel. In other words, the current
flowing through each first LED 111 is the same and the current
flowing through each second LED 112 is also the same.
[0015] As indicated in FIG. 2, the driver circuit 130 is a double
output driver circuit. The double output driver circuit is capable
of outputting a first driving current 131 to drive the first group
of light emitting elements 110 and a second driving current 132 to
drive the second group of light emitting elements 120. The
magnitude of the first driving currents is equivalent to or
different from that of the second driving current. The magnitude of
the first and the second driving currents can be independently
modulated through a color temperature controlling interface (not
illustrated) coupled to the driver circuit 130.
[0016] In addition, the color temperature controlling interface can
provide different driving currents to the first group of light
emitting elements 110 and the second group of light emitting
elements 120 to mix light. In an embodiment, the first color
temperature light emitted from the first LEDs 111 is warm white,
and the second color temperature light emitted from the second LEDs
112 is cool white. In an embodiment, the first color temperature
light emitted from the first LEDs 111 is cool white, and the second
color temperature light emitted from the second LEDs 112 is warm
white.
[0017] Suppose the first color temperature light emitted from the
first LEDs 111 of the first group of light emitting elements 110 is
warm white (color temperature 2700-3000K) and the second color
temperature light emitted from the second LEDs 112 of the second
group of light emitting elements 120 is cool white (color
temperature 6000-6500K) and the output ratio between the first
driving current and the second driving current is 7:3. Then, the
first color temperature light and the second color temperature
light can be mixed to obtain a near pure white light (color
temperature 4000-5000K).
[0018] Apart from the above mixing light mode, single color
temperature mode, such as the first color temperature mode or the
second color temperature mode, can be selected through the color
temperature controlling interface. When the first color temperature
mode is selected, the first driving current is the maximum and is
used to drive the first color temperature light (such as warm
white) emitted from the first LEDs 111 of the first group of light
emitting elements 110. However, to avoid dark band occurring
between every two first LEDs 111, a tiny amount of second driving
current is outputted to the second LEDs 112, wherein the second
driving current is the minimum but not equal to zero. Therefore, in
the first color temperature mode, the first driving current is the
maximum and the second driving current is the minimum but not equal
to zero. For instance, the output ratio between the first driving
current and the second driving current is 100:5. Thus, the second
LEDs 112 (referring to FIG. 1) between two first LEDs 111
compensates the dark band between two first LEDs 111 with low
brightness to increase overall light uniformity of the light
emitting device 10. Since a second LED 112 used for compensating
brightness is contained between every two first LEDs 111, the
interval between LEDs does not need to be too small, so that
manufacturing complexity and cost can be reduced. In practical
application, the interval between LEDs can be adjusted according to
actual needs.
[0019] Similarly, when the second color temperature mode is
selected, the second driving current is the maximum, and is used to
drive the second color temperature light (such as cool white)
emitted from the first LEDs 112 of the second group of light
emitting elements 120. However, to avoid dark band occurring
between every two second LEDs 112, a tiny amount of first driving
current is outputted to the first LEDs 111, wherein the first
driving current is the minimum but not equal to zero. Therefore, in
the second color temperature mode, the second driving current is
the maximum and the first driving current is the minimum but not
equal to zero. For instance, the output ratio between the second
driving current and the first driving current is 100:5.Thus, the
first LEDs 111 (referring to FIG. 1) between two second LEDs 112
compensates the dark band between two second LEDs 112 with low
brightness to increase overall light uniformity of the light
emitting device 10.
[0020] The light emitting device uses a driver circuit to output
different ratio of current to two groups of light emitting
elements. Regardless being in the mixing light mode or the single
color temperature mode (the first color temperature mode or the
second color temperature mode), two groups of LEDs will illuminate
to reduce the occurrence of bright band and dark band and increase
light uniformity. Emitting lights with different color temperatures
can be obtained through mixing when the much more different light
emitting units are used.
[0021] While the invention has been described by way of example and
in terms of the preferred embodiment (s), it is to be understood
that the invention is not limited thereto. On the contrary, it is
intended to cover various modifications and similar arrangements
and procedures, and the scope of the appended claims therefore
should be accorded the broadest interpretation so as to encompass
all such modifications and similar arrangements and procedures.
* * * * *